Solar thermal for hot-water (SHW) is a renewable energy application that harnesses heat from the sun to provide hot-water and heating in buildings. SHW systems are relatively straightforward to retrofit into buildings, can store heat for use at night, and even produce energy on cloudy days. With minimal maintenance and reasonable paybacks, SHW in the right application can offer a creative and cost-effective way to reduce greenhouse gas emissions.

How does it work?As shown in the photo to the right, each of the two solar collectors is made up of thirty high-efficiency, twin glass evacuated tubes. A transfer liquid absorbs the heat collected by the tubes and circulates it through a series of insulated pipes to a hot-water storage tank. Glycol, an anti-freeze fluid, is used as the heat transfer fluid instead of water to allow the system to operate year round.

In the summertime, a solar hot water system is typically expected to fully meet the hot water needs of a facility. In the winter, a natural gas-fired hot water heater serves as back-up. The solar hot water storage tank pre-heats the water, and the gas-fired tank raises it to a final temperature between 120 and 124 degrees F.

The New York Fire Department (FDNY) is leading the City's deployment of this technology through its pilot of SHW at Emergency Medical Station (EMS) 19 in the Bronx, shown to the left. Installation of two 30-evacuated tube collectors, piping, and hot-water storage tank was completed by FDNY in January 2009. Even in spite of a colder winter, the system saved 1,275 therms of natural gas and nearly $2,000 dollars in its first year of operation. Building on these successes, the City has applied for and was awarded funds for SHW systems at five additional firehouses in Far Rockaway and has applied for $425,124 to fund 13 more installations. Design for the five grant-funded systems and a large installation at Department of Parks and Recreation's St. Mary's Recreation Center in the Bronx are underway. In June, FDNY will complete another installation at Engine Company 298, for a total of eight systems in the works.